Vehicles, e.g., automobiles, generally have four wheels; i.e., two front wheels and two rear wheels, and can have an electronic control device for driving the wheels.
Japanese Laid-open Patent Application (JP-A) No. 2006-256605 discloses a four-wheel-drive electronic control unit (4WD-ECU) as such an electronic control device. The 4WD-ECU disclosed in Japanese Laid-Open Patent Application No. 2006-256605 together with a vehicle stability assist (VSA)-ECU controls the drive force that acts on the vehicle; and, specifically, sets the four-wheel-drive force in terms of units of, e.g., torque.
The VSA-ECU disclosed in JP 2006-256605 A sends to the 4WD-ECU a request, e.g., a torque-limiting request value for limiting each of the four wheel drive forces. The 4WD-ECU can reduce wheel torque (each of the four wheel drive forces) in accordance with such a torque-limiting request value. The VSA-ECU can thus limit the drive force that acts on a drive wheel of a vehicle.
A VSA-ECU or other vehicle behavior control means can generally be provided with at least one function from among a function for suppressing spinning of wheels (traction control system), a function for suppressing locking of wheels (antilock brake system), and a function for suppressing side-slipping of a vehicle.
Japanese Laid-open Patent Application (JP-A) No. 02-306865 discloses a vehicular false speed generating device (estimated speed generation device) used as control means including, e.g., a function for suppressing wheel spinning, a function for suppressing wheel locking, and other functions.
The vehicular false speed generating device disclosed in the lower right column of page 3 of JP 02-306865 A is provided with an adder 20e for calculating a center-of-mass acceleration correction value Gc which offsets the center-of-mass acceleration G by an amount equal to an offset value (e.g., 0.3 G).
Thus, in the case that the offset value is added to the vehicle acceleration (e.g., center-of-mass acceleration G) to obtain a corrected acceleration (e.g., center-of-mass acceleration correction value Gc), the corrected acceleration becomes greater than the acceleration prior to correction. Therefore, the present inventor recognized that the estimated speed may be calculated to be greater than the true speed in the case that the estimated speed of the vehicle is calculated on the basis of the corrected acceleration.